This invention relates to inserting linings into pipes particularly, but not exclusively, to the insertion of a preformed lining into an underground gas service pipe extending from an underground gas main to a building.
The terms `lining` and `liner` are used herein to include any insert which is capable of conveying a fluid within the pipe, and the insert may or may not be a close fit in the pipe.
Gas service pipes were made of steel or copper and they can be subject to corrosion in the ground and then leak. A procedure has been devised and is widely used for lining such gas services with a plastics tube. The procedure involves excavating a hole in the road or pavement to expose the connection between the gas service and the gas main, removing the section of service adjacent to the connection, pushing a length of plastics tube through the remaining length of service, and effecting connections at opposite ends of the plastics tube respectively with the main and with a meter cock.
In order to stop gas, in the event of a fire, spreading along the service by way of the annular space between the external surface of the plastics tube and the internal surface of the old service, that annular space in the end region of the service adjacent to the meter is filled with a predetermined quantity of sealant material, sufficient to fill totally the vertical limb of the service to provide a half-hour fire resistance.
The present invention is aimed at avoiding the need in most cases to excavate a hole to expose the connection between the main and the service. Such holes are costly to produce and fill, and can be very inconvenient to the public.
Whilst the invention is primarily concerned with gas pipes, it might be applied to water pipes or pipes conveying other liquids.